The present invention relates to a developing apparatus mounted, for example, on a copying machine to which electrophotography is applied, to a printer, and the like.
An electrophotographic copying machine includes, for example, a four-color developing apparatus. A color toner image is formed on a photosensitive belt by the four-color developing apparatus, and transferred to a sheet via an intermediate transfer drum.
This type of electrophotographic copying machine is preferably designed so that a moving direction of the sheet in a contact portion of the photosensitive belt and a developing roller is extended upwards from below in order to advantageously convey the sheet.
Moreover, there is provided a developing apparatus including a supply roller for supplying toner in contact with the developing roller, and a toner supply chamber disposed below the supply roller. The toner supply chamber is constituted of a guide plate disposed below the supply roller, and a sheet member disposed between the guide plate and the developing roller.
However, the conventional developing apparatus has the following problem.
That is, a toner is accumulated in a space formed by four members, that is, the guide plate and sheet member forming the toner supply chamber, the developing roller and the supply roller. Furthermore, a new toner is pushed into the space with the toner accumulated therein by rotation of the supply roller, and therefore, the toner is excessively accumulated. This causes a problem that a driving torque of the supply and developing rollers increases.
Moreover, the uncharged toner accumulated on the sheet member is directly supplied onto the developing roller. The uncharged toner has a small adhesion to the developing roller. As a result, a layer formation defect is generated in a nip portion between a layer thickness regulating blade and the developing roller. There is a problem that toner spilling easily occurs particularly in a region with a peripheral speed of the developing roller exceeding 250 mm/s.
The present invention has been developed in consideration of the aforementioned situation, and an object thereof is to provide a developing apparatus in which a developer can be supplied between a supply roller and a developing roller without being excessively accumulated, and an uncharged developer is prevented from being directly fed between a developing roller and a layer thickness regulating member.
According to the present invention, there is provided a developing apparatus comprising: a developing roller which is brought in contact with an image bearer, and rotates upwards from below in a contact portion to supply a developer to the image bearer; a supply roller which is brought in contact with the developing roller, and rotates in the same direction as that of the developing roller to supply the developer to the developing roller; a carrying device for carrying the developer to the supply roller; a retaining member which is positioned below the supply roller and disposed apart from the developing roller, and which retains the developer carried by the carrying device and allows the retained developer to be supplied to the developing roller by the supply roller; and a layer thickness regulating member for regulating a layer thickness of the developer supplied onto the developing roller.
According to the present invention, there is further provided a developing apparatus comprising: a developing roller which is brought in contact with an image bearer, and rotates upwards from below in a contact portion to supply a developer to the image bearer; a supply roller which is brought in contact with the developing roller, and rotates in the same direction as that of the developing roller to supply the developer to the developing roller; a carrying device for carrying the developer to the supply roller; a guide member which is positioned below the supply roller and disposed apart from the developing roller, and which guides the developer carried by the carrying device to the supply roller; an auxiliary guide which is disposed between the guide member and the developing roller, and which guides the developer fed from the guide member by rotation of the supply roller to the developing roller; and a layer thickness regulating member for regulating a layer thickness of the developer supplied onto the developing roller. The auxiliary guide has a structure for dropping a part of the developer downwards during guiding of the developer, and a tip end of the auxiliary guide in a guide direction of the developer is allowed to abut on the developing roller. The abutment portion is constituted of a macromolecular material, the developer on the developing roller is preliminarily charged, and a layer thickness of the developer is regulated.
According to the present invention, there is also provided a developing apparatus comprising: a developing roller which is brought in contact with an image bearer, and rotates upwards from below in a contact portion to supply a developer to the image bearer; a supply roller which is brought in contact with the developing roller, and rotates in the same direction as that of the developing roller to supply the developer to the developing roller; a carrying device for carrying the developer to the supply roller; a guide member which is positioned below the supply roller and disposed apart from the developing roller, and which guides the developer carried by the carrying device to the supply roller; an auxiliary guide which is disposed between the guide member and the developing roller, and which receives the developer falling from the contact portion between the developing roller and the supply roller and guides the developer to the developing roller; a movement regulating member for regulating movement of the developer to the auxiliary guide from the guide member; and a layer thickness regulating member for regulating a layer thickness of the developer supplied onto the developing roller.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.